Your DL media is actually made by CMC Magnetics a low cost/lower quality supplier. If the other fixes don't work, try some Verbatim +RDL media labeled Made in Singapore. It's the best by far.

I wouldn't ever recommend copying on the fly with Nero or any other program. It's best to rip (copy) the disk to be copied to your hard disk drive first and then go from there. If the disk is copy protected you'll need to rip with DVDFab HD Decrypter first or have AnyDVD running in the background removing protection.

I also am not a big proponent of burning DL disks with Nero. I prefer the free burning engine ImgBurn. Just use whatever authoring software you want and create an ISO image file and then burn the ISO with ImgBurn.

If you have a nonprotected DL disk you are trying to copy, jsut use DVD Decrypter (free). Set the mode to ISO Read and rip the disk to be copied to your HDD. Then set the mode to ISO Write, select the disk image created in step one or its companion MDS file and burn that to disk.